The editorial, titled 'A President's Credibility', was especially critical of his unproven claim that former president Barack Obama had authorised wiretapping Trump Tower in 2016.

"The President clings to his assertion like a drunk to an empty gin bottle, rolling out his press spokesman to make more dubious claims," the editorial said.

Mr Trump has not changed his allegation, despite FBI director James Comey testifying to the US Congress this week he does not have "any information" that supports it.

"Two months into his presidency, Gallup has Mr Trump's approval rating at 37 percent. No doubt Mr Trump considers that fake news, but if he doesn't show more respect for the truth, most Americans may conclude he's a fake President," the editorial said.

It comes not long after the paper's opinion page editor quit "following tensions over the section drifting in a pro-Donald Trump direction," US magazine The Atlantic reported.

Mr Trump's approval rating has sagged to 37 percent, according to a Gallup poll this week.

His first two months have been dominated by controversies from the firing of national security adviser Michael Flynn to his claim that Mr Obama wiretapped Trump Tower.